1. Field of the Invention
The present invention relates to a vacuum pump for generating high vacuum and including a housing having a gas inlet opening and a gas outlet opening, a shaft arranged in the housing, bearing means provided in the housing for supporting the shaft, drive means for rotating the shaft, and a plurality of pumping units arranged in the housing and formed each of rotational and stationary gas delivery components, with rotational components being supported on the shaft and the stationary components being connected with the housing.
2. Description of the Prior Art
For obtaining a high vacuum, combinations of different types of vacuum pumps are necessary. This is because a wide pressure range between the atmospheric pressure and the high vacuum pressure encompasses several flow regions in which the physical characteristics of conditions and flow regions of gases are subjected to different laws of physics.
Thus, for obtaining a high vacuum, at least two vacuum pumps of different types and with different operational characteristics are required, which are connected so that a single pump stand is formed. Known are pump stands formed of a turbomolecular pump, which is used as a high vacuum pump, and a vane rotary pump dischargeable in atmosphere. Pump stands formed of at least two vacuum pumps necessary for obtaining the required vacuum-technical values such as pressure ratio and suction or pumping speed, have serious drawbacks. These pump stands are expensive and require a large floor space. Each pump requires its own drive system with necessary current supply, monitoring and control, and requires its own bearing system.
For generating or obtaining high or ultra high vacuum, turbomolecular pumps found a wide application. However, the field of their use is limited by the achievable high pressure. Because of their operational characteristics, they can operate effectively only at pressures up to about 10xe2x88x923 mbar.
In the transitional pressure region between the high pressure and the atmospheric pressure, in multi-stage systems, regenerative pumps can be used. They can easily be combined with turbomolecular pumps and other molecular pumps. The rotor elements of both pumps, e.g., of a turbomolecular pump and regenerative pump can be mounted on a common shaft, forming a unitary assembly.
However, the transition from a turbomolecular pump stage or another molecular pump stage and a regenerative pump stage cannot be carried out smoothly. The compression of the turbomolecular pump stage decreases with increase in pressure, and a compression of a regenerative pump stage decreases at a lower pressure. Thus, the operational regions of both pump stages practically do not intersect.
The lack of compression in the transitional region between the molecular pump stage and the regenerative pump stage can be made up with Gaede stages. However, the Gaede stage has a very low suction or pumping speed in comparison with a turbomolecular pump stage. Therefore, only a small portion of the gas volume delivered from the last stage of the turbomolecular pump can be delivered further. Thus, the total suction or pumping speed of the pump combination is substantially reduced.
Accordingly, an object of the present invention is to .provide a vacuum pump encompassing the entire pressure region from the atmospheric pressure up to the high and ultra high vacuum region.
Another object of the present invention is to provide a vacuum pump encompassing the above-mentioned pressure region, formed as a unitary assembly, and having a compact structure, and in which the drawbacks, which characterize pump stands formed of several pumps, are eliminated.
A further object of the present invention is to provide a vacuum pump, as described above, and having satisfactory pressure ratios and suction speeds capable of meeting the requirements of practical applications of such pumps. The vacuum pump should be reliable in operation.
These and other objects of the present invention, which will become apparent hereinafter, are achieved by providing a vacuum pump having a plurality of pumping units arranged in the housing and formed each of rotational and stationary gas delivery components, with the rotational components being supported on the shaft and the stationary components being connected with the housing, with at least one of the pumping units being form of a plurality of connected parallel to each other and arranged one after another in an axial direction, molecular pumping stages each formed based on Gaede principle, and with common connection channels for connecting the molecular pumping stages with each other in such a way that a parallel delivery of a compressed gas takes place.
The parallel connection of the Gaede pump stages according to the present invention permits to obtain a compact vacuum pump covering the entire pressure region from the atmospheric pressure to the high and ultrahigh vacuum. The combination of small pumping units, which is obtained by the use of Gaede pump stages connected in parallel and seriesly, permits to achieve optimal pump characteristics and an effective operation. The suction speed at the suction opening can be optimally used over the entire pressure region as the pressure consistency can be so established that the gas amount is delivered from a preceding pumping unit or pump stage to a following pumping unit or stage without any losses. The advantages of the present invention are particularly achieved when the parallel Gaede stages are combined with a turbomolecular pump or with a regenerative pump, or with both pumps.
The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiments, when read with reference to the accompanying drawings.